1. Field of the Invention
This invention relates to fan filter units useful in clean rooms and like applications. More particularly, the invention relates to a fan filter unit that simultaneously achieves all the major objectives for such a unit:
1. Filtration efficiency of 99.999% at 0.12 micron particles, at
2. Air flows of about 90 FPM,
3. Energy usage of about 100 watts, and
4. Lower BTU output for reduced air conditioning load.
Fan filter units typically are suspended individually or in banks above a workspace, each individual fan filter unit combines a motorized fan, a fan enclosure supporting the fan, and filter media in a filter unit downstream from the fan enclosure all arranged to introduce, e.g. HEPA or ULPA filter-processed air into the workspace environment. The invention advantageously uses a filter pack of relatively increased depth, e.g. 5 inches of depth and greater, no metal separators, and increased pleat count, e.g. 5 to 7 pleats per inch, for maximum energy efficiency. Prior art fan filter units use more energy, are less efficient, and comprise, typically, less deep packs, e.g. 2-4 inches in depth.
2. Related Art
Known filter fan units are desirably improved in terms of filtration efficiency, quietness of operation and energy efficiency including both energy consumed directly by the filter units to drive the fans and energy consumed indirectly by the units through heat output into the air-conditioned room. Achieving the one should not detract from achieving the other. Presently popular fan filter units use trough-like transverse baffles to redirect the air flow from a first direction, generally radially outward from the fan, to a second, opposite direction, generally toward the fan and within the height of the filter fan unit enclosure, see generally U.S. Pat. No. 5,470,363 to Leader et al. Reversing flow will usually entail excess energy consumption and prevent achieving of the desired low energy consumption of about 100 watts or less.